Ironically, ME2 is my least favorite of the trilogy, because plot-wise, it’s worse than just being a plot cul-de-sac because it undoes everything set up in 1 and sets ME3 up for failure by introducing more plot lines that have to be resolved. I know everyone loves it because of the characters and BioWare changing a lot of mechanics so it’s more fun to play, but I like the trilogy for the story, and ME2 really fails, story wise, as the middle part of a trilogy, because it doesn’t advance the story set up in ME1 - it ends with us in the exact same place, story-wise, only with more baggage. It’s got a great series of individual stories and is good as an anthology, but hurts the overall story of the trilogy.
I really love this video on it, since it really explains how ME2 wasn’t actually good for story of the trilogy: Mass Effect 2 Broke the Franchise.